FR2694605A1 - Control assembly for a plurality of hydraulic receivers. - Google Patents

Abstract

The hydraulic receivers are supplied by the same generation of flow (71), each being connected to it via a proportional distributor (70), the assembly comprising at least one auxiliary valve (303) supplied by the generation of flow. (71) and producing a pressure normally equal to a regulating pressure increased by a constant, and in each proportional distributor actuating means cause the compensating spool (16) to respond to the pressure produced by the auxiliary valve.

Description

i The invention relates to a control assembly of a plurality of

  hydraulic receivers, through which

  the receivers are supplied by the same generation of flow, each being connected to it via a proportional distributor.

  We know that distributors are devices that are available between a flow generation and a receiver

  to control the operation of the receiver by adapting the way it is connected to the flow generation. 10 The proportional type distributors

  try not only a controlled drawer whose position determines the section of a constriction, but also a drawer

  automatic compensator to keep the difference constant

  pressure pressure between the upstream and downstream of this choke

  ment, so that at a given position of the controlled drawer corresponds to a given flow of fluid Consequently, when a receiver is controlled with a proportional distributor, its operating speed is fixed by the position of the controlled drawer, regardless of the load that

supports the receiver.

  When the flow generation is used to supply a plurality of receivers to each of which corresponds a proportional distributor, it may happen that the total flow requested by the receivers exceeds the flow

  that flow generation is able to provide.

  The respective compensating drawers are no longer in

  able to maintain the different

  pressure between the upstream and downstream of the throttle at the prefixed constant, so that the most loaded receivers slow down or stop while the least loaded can continue to operate. To avoid these disorders, it has already been proposed to take advantage of the regulation of the generation of flow according to the requested power, which is currently provided on most of the hydraulic circuits where the

  flow generation feeds a plurality of receivers.

  This regulation is carried out by providing so-called "load-sensing" load detection means which reduce the pressure of the most loaded receiver towards the generation of flow,

  to which pressure responds the generation of flow in product

  sant a working pressure equal to the load-

  sensing plus a constant In reality, this cons-

  aunt is added as long as the total demand for debit is less than that capable of being supplied, but in case of excess

  of demand, the value added to the load-

  sensing is smaller than the constant, and all the smaller that the excess demand for debit is important It is this decrease in the added value which we take advantage of

  to avoid the aforementioned disorders.

  FR-A-2 339 757 proposes to act on pressure

  actuation of the drawer ordered in each of the dispensers

  proportional, by providing that the operating valves

  are no longer supplied directly from a pilot pump, but with interposition between the pilot pump and the actuation valves of a margin-of-maneuver valve which varies the supply pressure of the control valves of the same way the difference between

  flow generation pressure and load pressure

  sensing As long as the flow generation works normally-

  The supply pressure of the control valves remains constant, just as if these valves were supplied directly by the pilot pump. In case of excessive flow demand, the supply pressure of the control valves will decrease depending on the importance of excess demand, the operating pressure of all the ordered drawers will decrease in the same way, and consequently all the throttles produced by the ordered drawers will increase in the same way, with the result that each distributor will be applied the same rate reduction rate so that all receivers will

  slow down with conservation of their gear ratio.

  FR-A-2 548 290 proposes to achieve the same result in the case where the proportional distributors have a compensating drawer which is located upstream of the controlled drawer, by acting on the actuating means of the compensating drawer: it continues to be used in the direction of closing by the pressure upstream of the controlled drawer and in the direction of opening by the pressure downstream of the controlled drawer, but the conventional spring is replaced by a double pressure stress, respectively in the direction of closing by the load-sensing pressure and in the opening direction by the pressure of the flow generation La

  pressure difference between upstream and downstream of the choke-

  the controlled drawer is thus controlled by the difference between the pressure of the flow generation and the pressure of

  load-sensing, which leads to the aforementioned result.

  The invention aims to obtain this same result, but

with improved performance.

  To this end, it offers a control assembly for a plurality of hydraulic receivers, through which the receivers are supplied by the same generation of flow, each being connected thereto by means of a proportional distributor comprising: a controlled drawer whose the position determines the section of a first constriction;

  a compensating drawer to regulate the difference

  pressure rence between the upstream and downstream of said first throttle by producing upstream thereof a second throttle of appropriate section; and

  means for actuating the compensated drawer

  tor, to make it automatically assume a position where it produces said second throttle of appropriate section, in response to several pressures acting respectively in the direction of opening and in the direction of closing; set characterized in that it comprises in

  in addition to at least one auxiliary valve supplied by the genera-

  tion of flow and producing a pressure normally equal to a regulating pressure increased by a constant, and in that in each proportional distributor said means for actuating the compensating slide are provided so that it is acted upon: in the direction of the opening by the pressure downstream of the first throttle and by the pressure produced by a said auxiliary valve; and in the direction of closing by the pressure upstream of the first constriction, by said pressure of

  regulation, and by a substantially constant force.

  In the case where the regulating pressure is the load sensing pressure, the assembly according to the invention differs from that described in the last prior art cited above by the presence of the auxiliary valve whose pressure produced is applied in place of the pressure of

flow generation.

  In reality, to carry out the prior assembly in a practical manner, it would have been convenient to apply the pressure upstream thereof to the compensating slide rather than the pressure of the flow generation. When the distributors are distributed in different places d '' a machine, however, difficulties would arise because the pressure upstream of the second throttle is not the same in the respective distributors, due to different pressure losses between the generation of flow and the

respective distributors.

  Similar difficulties would also occur with the different distributors of a control block located at a distance from the flow generation, the pressure drops between the latter and the block increasing with the flow in the block supply pipe: it could for example happen that the controlled drawer of one of the block distributors remains in the same position, and that the flow passing through it decreases without there being an overshoot of the flow capacity This would happen in particular by following an increase in the flow rate passing through a second distributor because the increase in the total flow rate of supply to the block increases the pressure losses between the generation of flow rate and the block, and therefore decrease the difference between the pressure d food

  block (i.e. pressure upstream of the second choke

  all distributors in the block) and the pressure

load sensing.

  The assembly according to the invention makes it possible to avoid

this difficulty.

  The invention also offers the advantage of being able to provide the desired result even if the generation of flow is not regulated as a function of the load supported by the receivers. Preferably, for reasons of simplicity and convenience, the auxiliary valve comprises:

  a feed chamber connected to the genera-

  flow rate; a regulation chamber in which said regulation pressure prevails; an outlet chamber o reigns said pressure produced; a drawer whose position determines the section of a throttle between the supply chamber and the outlet chamber, comprising a first active surface disposed in the regulation chamber so that said regulation pressure acts in the direction of opening , and a second active surface arranged in the outlet chamber so that the pressure produced acts in the closing direction; and

  a spring, which acts on the drawer in the opening direction.

  In the case where the proportional distributors are divided into several groups of a distributor or several neighboring distributors, the groups being distant from each other, it is preferable that the assembly includes

  for each group an auxiliary valve adjacent to the group.

  This avoids problems related to pressure drops in line, and especially to have to provide a line between the auxiliary valve and a group of distributors distant from the latter. The disclosure of the invention will now be continued

  by the description of exemplary embodiments, given below

  by way of illustration and not limitation, with reference to the accompanying drawings, in which: Figure 1 is a schematic sectional view of a proportional distributor forming part of an assembly according to the invention;

  Figure 2 is a diagram of a hydraulic circuit

  lique comprising this control assembly, which comprises two distributors similar to that shown in Figure 1, joined end to end; and Figures 3 and 4 are similar to the figures

  1 and 2 respectively, but for an alternative embodiment.

  The distributor 70 illustrated in FIG. 1 is similar to that described in FR-A-2,562,632, with the exception

  of its pressure compensating device.

  It comprises a stator block 1, in the bore 2 of which slides a cylindrical controlled drawer 3 In the usual way, the switching of the hydraulic circuits is effected by displacement of the grooves of the drawer 3 in front of

stator lights.

  At its left end, for example, the drawer 3 is provided with a spring return device of known type, comprising a helical spring 4, compressed between the shoulders 5 and 6 of two rings 7 and 8, trapped between two shoulders of the end 9 of the drawer 3, around which they can slide Thus, the drawer 3 is spontaneously returned to a neutral rest position, while it is pushed to the right (FIG. 1) when a pilot pressure is sent in an opening 10 in the fixed bonnet 61 On the contrary, it is pushed to the left when a pilot pressure is sent opposite, in an opening 11 in the bonnet 62 at its other end In the example illustrated, it has been assumed that the three-position slide 3 is used to control a double-acting hydraulic cylinder 12 For this, one of the sections of the cylinder 12 is connected to a first use channel 13 of the stator 1, while the opposite section of cylinder 1 2 is connected

  to a second use pipe 14 of the stator 1.

  The distributor receives in an annular chamber

  , the pressure sent by a generation of flow 71.

  The supply chamber 15 surrounds a compensating drawer 16, also called a balance, which is movable in a bore 80 of the stator 1 The drawer 16 is provided with a radial bore 22 communicating with a blind axial bore 23 The latter opens onto a seat capable of being closed off or unmasked by a ball 24 whose return spring 25 is compressed inside the compensating drawer 16 The chamber containing the ball 24 and the spring 25 opens out through a lateral opening 26 in an annular chamber 27

  surrounding the central part of the drawer 3.

  At each of its two ends, the controlled drawer 3 has an axial internal housing, 28 on the left,

29 right.

  The housing 28 communicates with the outside of the drawer by two radial holes referenced respectively 30 and 31 Likewise, the housing 29 opens onto two holes

radials 32 and 33.

  When the drawer 3 is in its neutral rest position, the bore 30 faces a solid part 34 of the

  stator closing it, between two annular chambers 35 and 36.

  The chamber 35 communicates with the first use pipe 13, while the chamber 36 is connected to the return circuit. Similarly, the bore 32 is closed at rest, by a solid part 37, located between two annular chambers

  38 and 39 Room 38 communicates with the second channel-

  tion of use 14, while the chamber 39 is connected to the

return circuit.

  Between the holes 30 and 31, the stator defines, in the bore, a solid part 40, in front of which is

  likely to move a groove 41 of the drawer 3.

  Around drawer 3, in the area around hole 31 when drawer 3 is pushed to the right (figure

  1), there is an annular stator chamber 42.

  Similarly, at its opposite end, the drawer 3 has a groove 43 movable in front of a solid part 44 of the stator Around the passage 33 when the drawer 3 is pushed to the left, there is an annular stator chamber 45. The two chambers 42 and 45 are connected by a

  line 46 known as load sensing line.

  Progressives notches equip the different grooves of the drawer, as indicated for example by

references 48, 49, 50, 51.

  Finally, a first booster valve 52 is mounted

  in parallel on the first use pipe 13.

  Similarly, a booster valve 53 is mounted in parallel on the second use pipe 14 Behind the valves 52 and 53, there is a chamber 54 connected to the circuit of

oil return.

  A pressure relief valve, respectively 55 and 56, is provided on the side of each of the use pipes 13, 14, which can thus flow into the

  return chambers, respectively 36, 39.

  The operation of the controlled drawer 3 will

now be described.

  In the neutral position, the chambers 27, 35 and 38 are closed, so that the jack 12 is immobilized while no flow passes through the distributor. In addition, the

  line 46 communicates through grooves 41 and 43 respectively.

  with room 36 and room 39, that is to say

  that it is connected to the return circuit.

  When a pilot pressure is sent through the opening 10, as is the case in FIG. 1, the slide 3 slides to the right with an amplitude determined by the value of the pilot pressure, which is balanced with the opposing thrust of the spring 4, more or less compressed The supply pressure of the chamber 27 is sent into the pipe 13 passing through the groove 49 and the room 35, while the pipe 14 communicates with the return chamber 39 by the groove 51 Each of the grooves 49 and 51 determines a constriction the cross section of which is determined by the position of the drawer 3 In addition, the pipe 46 communicates on the left with the pipe 13 through the passages 31, 28 and 30, while on the right it is closed The pressure downstream of the throttle provided by the groove 49

  is thus transmitted to line 46.

  When a pilot pressure is sent through the opening 11, the slide 3 slides to the left to a position determined by the amplitude of the pilot pressure The supply pressure of the chamber 27 is sent into the pipeline 14 through the groove 50 and the chamber 38, while the pipe 13 communicates with the return chamber 36 through the groove 48 Each of the grooves 48 and 50 determines a constriction whose section is determined by the position of the drawer 3 In addition, the pipe 46 communicates on the right with the pipe 14 through the holes 33, 29 and 32, while on the left it is closed. The pressure downstream of the throttle provided by

  the groove 50 is thus transmitted to the pipe 46.

1 O

  It can thus be seen that in the neutral position, the channeling-

  tion 46 is put under the pressure of the return circuit, while in each of the working positions, it is brought to the pressure downstream of the throttle provided by the slide 3 on the supply line of the jack 12, it that is to say at the operating pressure thereof.

  The circuit selector 99 (also called the OR function) has one of its inputs which communicates with the pipe-

  tion 46 by a channel 72, and its other inlet which communicates with a channel 73 connected to the outlet pipe of the circuit selector of a similar distributor. Here, the pressure in the pipe 46 is the strongest, so that the selector of circuit 99 adopts the position illustrated o it transmits by its output to the pipeline 74 the operating pressure of the jack 12, which is the highest operating pressure of all the receivers that the flow generation 71 supplies More generally, as clearly appears in FIG. 2, it is always the pressure of the most loaded receiver which is applied to the pipe 74, this pressure called "load sensing" being transmitted to the generation of flow 71 which produces a operating pressure normally equal to load pressure

sensing plus a constant.

  The compensating slide 16 comprises around the channel 22 a groove 111 which produces, depending on the position of the slide, a more or less significant constriction upstream of the constriction provided by the slide 3 on the supply line of the jack 12, depending on the position taken

by drawer 16.

  This has two active surfaces, on the left

  a surface 112 subjected to pressure upstream of the constriction

  provided by drawer 3, and on the right a surface 301

  subject to the pressure prevailing in line 46,

  i.e. at the operating pressure of the jack 12.

  On the left side of the drawer 16 is disposed a piston 114 movable coaxially, which comes into contact with the drawer 1 1 compensator by a stud, and slides in a cylinder 116 screwed into the stator 1 coaxially with the bore 80, the cylinder 116 being open from the inside and closed from the side

  outside, and sealingly crossing the pipe 46.

  The piston 114 has an L-shaped passage which makes it possible to communicate the chamber 115 situated between the piston and the bottom of the cylinder with the pipe 119, which is connected to the load-sensing pipe for the generation of flow, so that it is brought to the load sensing pressure The piston 114 has two opposite surfaces, a surface 121 facing the active surface 112 of the drawer 16, and subjected to the same pressure, and an active surface 123 subjected to the

load sensing pressure.

  A spring 125, the force of which is adjustable with

  the screw 126, applies the piston 114 against the drawer 16.

  This comprises on the right a third active surface 302 which is subjected to the pressure produced by a

auxiliary valve 303.

  The surfaces 301 and 302 look to the right, and the pressures to which they are subjected stress

  the drawer 16 in the opening direction.

  The surface 301 is subjected to the pressure prevailing downstream of the throttle provided by the slide 3 because it is disposed in the pipe 46, and the surface 302 is subjected to the pressure produced by the valve 303 because it is arranged in a chamber 304 connected by a

line 305 to valve 303.

  The surfaces 112 and 123 look to the left, the pressures to which they are subjected therefore urge the drawer 16 in the direction of closure. The surface 121 looking to the right, urges the piston 114 to the left, that is to say that everything happens as if the pressure

  upstream of the throttle provided by the drawer 3 applies

  quait on the effective value of the surface 112 minus the effective value of the surface 121 We will note 52 the effective value of this difference in active surfaces, which we will call for convenience "dimensioning of the active surface

  112 ", and 51 the effective value of the active surface 123.

  The effective value of the active surface 301 is

  also 52, and that of the active surface 302 is 51.

  If we also note F the force applied by the

  spring 125, Pl the pressure prevailing upstream of the choke

  ment provided by the controlled slide 3, P 1 S the load sensing pressure, PU the pressure prevailing downstream of the throttle provided by the controlled slide 3, and Pp the pressure produced by the auxiliary valve 303, it is shown that equilibrium Pi Pui = SI (Pp-P 1 ") S

  We see that the pressure difference Pl PU.

  depends on the pressure difference Pp P 1 S following a linear function with strictly positive coefficient and at

strictly negative constant.

  The auxiliary valve 303 comprises a stator body 306 which defines a supply chamber 307 connected to the discharge orifice of the flow generation 71; a regulation chamber 308 in which P 1 S prevails; an outlet chamber 309 where said pressure produced prevails; a drawer 310 whose position determines, thanks to a groove 311, the section of a constriction between the chambers 307 and 309; and a spring 312 which acts on the slide 310 in the opening direction, a screw 313 being provided for

  adjust the force with which the spring acts.

  P 1 S prevails in room 308 because this

  chamber is connected to line 74.

  The drawer 310 has a first active surface 314 disposed in the chamber 308, and therefore subject in the direction of opening to PIS and a second active surface 315 disposed in the chamber 309, which means that the pressure produced acts on the surface 315 in the closing direction We show, in case the effective value of surfaces 314 and 315 is similar, and if we write S this value and F the force exerted by the spring, that we obtain Pp = Pl S + F The pressure produced is therefore normally independent of the pressure supplied by the flow generation. In the case where the proportional distributors of the control assembly are divided into several groups of a distributor or of several neighboring distributors, the groups being distant from each other, for example in the case of a public works machine, divided into a first group of two distributors which control the right and left engines for advancing the vehicle, a second group of a single distributor which controls the rotation of a turret, and a third group of several distributors which control the different arms of the machine, it is preferable to provide an auxiliary valve for each group, not only to avoid pressure drop problems, but also to avoid having to provide a pipe between a valve

  centralized auxiliary and the different groups.

  FIG. 2 shows a control assembly according to the invention, formed of a single group of two contiguous distributors, respectively the distributor 70 illustrated in FIG. 1, and an identical distributor 70 ', all the elements of the latter carrying the same reference as

  the distributor 70, but assigned a prime index.

  It will be noted that the pipes 73 and 74 form with the selector 99 an assembly which crosses all of the

  distributor 70 and it is the same for the pipelines

  119 and 305, so that it is possible to make the connections between distributors, by simply joining

these last end to end.

  In the variant of the control assembly according to the invention shown in FIGS. 3 and 4, the same reference numbers have been kept for the identical elements while the number 100 has been added to them for the

similar items.

  The proportional distributor 170 shown in FIG. 3 includes a compensating drawer 116, the left part of which is different from that of the drawer 16: in the position illustrated in FIG. 3, the compensating drawer 116 closes the passage between the chambers 15 and 27, but when it moves to the left it produces, depending on its position, a more or less significant constriction upstream of the constriction provided by the drawer 3 on the line

cylinder supply 12.

  The drawer 116 has two surfaces 83 and 300 subjected to the pressure upstream of the throttle provided by the drawer 116, an active surface 84 subjected to the pressure upstream of the throttle provided by the drawer 3, and an active surface 85 subject to the pressure prevailing in a

  room 86 located to the left of drawer 116.

  The surfaces 83 and 300 are opposite and have the same dimensioning, the drawer 116 therefore does not react to the

  pressure upstream of the constriction it provides.

  Surfaces 84 and 85 look to the left.

  Since the drawer 116 closes the constriction it produces when it moves from the left to the right and vice versa, the pressures to which the surfaces 84 and 85 are subjected urge it in the closing direction A spring 87 is provided in the chamber 86 between the bottom of the latter, located on the left, and the surface 85, which means that the drawer 116 is also biased in the closing direction by a substantially constant force To adjust the latter , a screw 88 is provided which forms the bottom of

room 86.

  The surface 84 is subjected to the pressure prevailing upstream of the constriction provided by the drawer 3 because it is disposed in a chamber 91 communicating with the

room 27 via a duct 92.

  The drawer 116 is provided with a radial bore 93 communicating with a blind axial bore 94 which opens onto a seat capable of being closed off or unmasked by a ball 95 whose return spring 96 is compressed in a chamber 98 which opens out an axial opening 100 in the chamber 86 This communicates by a passage 101 with a pipe 102 closed at one end and opening into the reservoir for the generation of flow through a restriction 104 at the other end, the pipe 102 being common to all distributors, who have their room corresponding to

86 which is connected to it.

  It can be seen in FIG. 4 that for each distributor 170 and 170 ', the common pipe 102 is connected to the upstream of

  the throttle provided by the drawer 3 by means of a non-return valve, the ball 95 of which forms the shutter, this non-return valve passing

  towards the pipe 102 It reigns consequently in this one

  ci the highest of the pressures prevailing upstream of the throttles

  elements provided by the drawers 3 and 3 ', the restriction 104 realizing a decompression of the pipe 102 which allows the continuous adjustment of the latter to the maximum of the pressures upstream of the drawers 3 and 3' It is therefore this last pressure

  which prevails in room 86 and in the corresponding room

dante of the distributor 70 '.

  It is also this last pressure that reigns

  in room 308, since here it is connected to the canali-

sation 102.

  In the example illustrated, the surface 84 has a similar dimension to the surface 301, that is to say 52, and the surface 85 has a similar dimension to the surface

302, i.e. 51.

  Given the layout and size

  ment of surfaces 84 and 85, the action of the load sensing pressure has in fact been replaced by the maximum of the pressures prevailing upstream of the throttle provided by the slide

  ordered in the respective drawers, noted MAX (Pj).

  Provided that PI is replaced by MAX (Pj), the equations given above apply to the variant

shown in Figures 3 and 4.

  It will be noted that there is no non-return valve in the distributor 170 between the chambers 15 and 27,

unlike the distributor 70.

  In fact, we are sure that at rest, when all the ordered drawers 3 are neutral, that all the drawers

  compensators 116 are in the closed position illus-

  very: if we keep the same notations as before and by noting P the discharge pressure of the flow generation, by observing that Pp is at most equal to P and that at rest Pl = P in all the distributors, even if the drawer 116 is closed taking into account the minute leaks between the upstream and downstream thereof which are inevitable, we see that the drawer 116 is biased in the direction of closing by

F + P 51 + P 52

and in the direction of opening by

P 51.

  Since F + P 52 is strictly positive, we are sure that the forces acting in the direction of closure will always be greater than those acting in

the sense of openness.

  In service, in each of the illustrated assemblies, in the event that the total flow demand of the receivers 12 and 12 'exceeds that capable of being supplied by the flow generation 71, the speed ratios between receivers are maintained because in case of excess demand for flow, room 307 is not supplied with sufficient pressure for F / S to be added to PIS or to MAX (Pi), only a lower value is added, all the smaller

  that the excess demand for debit is large.

  The values 51, 52 and F are chosen in particular according to the following requirements: the drawer 16 or 116 must ensure in normal service, o P p MAX (Pj) or P p Pis = a, a value b to Pl PU so that : = If a _F

52 52

  the drawer 16 or 116 must close for a certain minimum value c of P p MAX (Pj) or of Pp P s, below which it is considered that the overload is too great for the speed ratios between the receivers can be maintained, so that 51.c = F. It is possible, depending on the circumstances, to choose a regulation pressure other than MAX (P;) or the load-sensing pressure. In these variants, the

  advantages of using an auxiliary valve.

  More generally, numerous variants can be made to the examples described. In this regard,

  recalls that the invention is not limited to the latter.

Claims (8)

  1 control assembly for a plurality of hydraulic receivers (12, 12 ′), through which the receivers are supplied by the same generation of flow (71), each being connected thereto by means of a proportional distributor comprising: a controlled drawer (3) whose position determines the section of a first constriction;   a compensating drawer to regulate the difference   pressure rence between the upstream and downstream of said first throttle by producing upstream thereof a second throttle of appropriate section; and   means for actuating the compensated drawer   tor, to make it automatically assume a position where it produces said second throttle of appropriate section, in response to several pressures acting respectively in the direction of opening and in the direction of closing; assembly characterized in that it further comprises at least one auxiliary valve (303) supplied by the   generation of flow (71) and producing normal pressure   equal to a regulation pressure increased by one   constant, and in that in each distributor proportion-   nel (70, 70 '; 170, 170') said means for actuating the compensating slide are provided so that it is acted upon: in the direction of opening by the pressure downstream of the first throttle and by the pressure produced by a said auxiliary valve (303); and in the direction of closing by the pressure upstream of the first constriction, by said pressure of   regulation, and by a substantially constant force.   2 assembly according to claim 1, characterized in that in each proportional distributor, said actuating means of the compensating slide comprise thereon a first active surface (301) subjected to the pressure downstream of the first throttle, a second active surface (302) subjected to the pressure produced by the auxiliary valve, a third active surface (84, 112) subjected to the pressure upstream of the first throttle, and a fourth active surface (85, 123) subjected to said regulating pressure, said first and second surfaces (301, 302) being opposite said third and fourth surfaces (84, 85; 112, 123); as well as a spring (87, 125) urging the compensating slide (16, 116) in the direction of closure.   3 assembly according to claim 2, characterized in that said first and third active surfaces (301, 84; 301, 112) of the compensating slide (16, 116) have a similar dimensioning, and in that said second and   fourth surface (302, 85; 302, 123) of the compensating drawer   have a similar size.   4 Assembly according to any one of the claims   cations 1 to 3, characterized in that said auxiliary valve (303) comprises: a supply chamber (307) connected to the generation of flow (71); a regulation chamber (308) in which said regulation pressure prevails; an outlet chamber (309) where said pressure produced prevails; a drawer (310), the position of which determines the cross section of a throttle between the supply chamber (307) and the outlet chamber (309), comprising a first active surface disposed in the regulation chamber (308) so that said regulating pressure acts in the direction of opening, and a second active surface (315) arranged in the outlet chamber (309) so that the pressure produced acts in the direction of closing; and a spring (312), which acts on the slide (310) in the direction of opening.   An assembly according to any one of claims 1 to 4, characterized, the proportional distributors being distributed in several groups of a distributor or of several neighboring distributors, the groups being distant from each other, in that it comprises for each group   a so-called auxiliary valve close to the group.   6 Assembly according to any one of the claims.   tions 1 to 5, characterized in that it includes means (73, 74, 99, 99 ') for detecting the pressure of the most loaded receiver, called "load sensing pressure" and in that the   regulating pressure is the load sensing pressure.   7 assembly according to claim 6, characterized in that the detection means comprise for each proportional distributor a pipe which connects the downstream of the first throttle to a circuit selector (99, 99 '),   and in that in case there are several select them   Circuit torers are arranged in cascade.   8 Set according to any one of the claims   1 to 5, characterized in that it includes means (95, ', 102, 104) for detecting the maximum of the pressures prevailing upstream of the first throttle in the respective proportional distributors (170, 170'), and in that that said regulating pressure is the maximum of the upstream pressures thus detected.   9 assembly according to claim 8, characterized in that in each proportional distributor (170, 170 ') there is absence of non-return valve between said second   strangulation and first strangulation.   An assembly according to any one of the claims   cations 8 or 9, characterized in that said means for detecting the maximum of the pressures upstream of the first respective throttles comprise a common pipe (102) closed at a first end and opening into the tank through a restriction (104) at a second end; and for each proportional distributor a non-return valve (95) disposed passing between the upstream of the   first strangulation and common conduct.